with_preamble method silently drops previously-set callback handlers

[coderabbitai]

Problem

The with_preamble method currently resets callback handlers to None when called, which can surprise users who have already registered success/failure callbacks.

Location

Lines 90-92 in src/server.rs

Current Behaviour

When a user calls with_preamble after setting callback handlers via on_preamble_decode_success or on_preamble_decode_failure, the previously-set handlers are silently dropped and reset to None.

Suggested Solutions

Either:

1. Document the required call order prominently in the API documentation
2. Carry the existing Arc<...> callback values across to the new instance to preserve user-set handlers

Context

This issue affects the user experience of the preamble callback API and could lead to unexpected behaviour where callbacks appear to be ignored.

References

• Pull Request: Implement preamble callback tests #28
• Review Comment: Implement preamble callback tests #28 (comment)

Reported by: @leynos